American Registry of Radiologic Technologists (ARRT) Practice Exam

Which of the following defines the photoelectric effect?

1. Scattering of photons

2. Absorption of photons with emission of electrons

3. Transformation of energy into mass

4. Interaction of photons with matter without absorption

The correct answer is: Absorption of photons with emission of electrons

The photoelectric effect is defined as the phenomenon where photons are absorbed by matter, leading to the ejection of electrons from that matter. This process occurs when a high-energy photon interacts with an atom and transfers enough energy to overcome the binding energy of an electron, resulting in the electron being emitted from the atom. This effect is significant in various fields, including medical imaging and radiation therapy, as it helps to explain how x-ray imaging materials absorb radiation and the interactions at play during such processes. In the context of the other options, scattering of photons does not involve absorption or ejection of electrons, but rather a change in direction of photons. The transformation of energy into mass relates to principles outlined by Einstein’s theory of relativity (E=mc^2), which is not applicable in the context of the photoelectric effect. Lastly, the interaction of photons with matter without absorption implies that no energy transfer occurs, which contradicts the definition of the photoelectric effect where absorption is a critical component. Hence, the absorption of photons with the subsequent emission of electrons accurately captures the essence of the photoelectric effect.